I2C-UART Bi-Directional Logic Level Converter 5V-3.3V 2-channel

Some modules operate with 3.3V I2C or UART, and this module can convert the voltage if your system operates at 5V (e.g., your 5V Arduino).

Additionally, there is a built-in voltage regulator that converts 5V to 3.3V up to 100mA, which is also useful if you need to power a module with 3.3V that does not have a built-in voltage regulator.

The pins are indicated on the bottom:

Connect AVCC to 5V
Connect ASCL to SCL/TX pin of 5V system
Connect ASDA to SDA/RX pin of 5V system
Connect AGND to GND of 5V system

Connect BVCC to 3.3V of system
Connect BSCL to SCL/RX pin of 3.3V system
Connect BSDA to SDA/TX pin of 3.3V system
Connect BGND to GND of 3.3V system

This module is in principle only suitable for converting from 5V to 3.3V. The voltage regulator can only convert 5V to 3.3V.
If your system is 3.3V and you want to connect a 5V module, you should connect it as follows:

Connect AVCC to 5V (5V power line)
Connect ASCL to SCL/TX pin of 5V system
Connect ASDA to SDA/RX pin of 5V system
Connect AGND to GND of 5V system

Do not connect BVCC
Connect BSCL to SCL/RX pin of 3.3V system
Connect BSDA to SDA/TX pin of 3.3V system
Connect BGND to GND of 3.3V system

Note: The pin headers for this module are not yet soldered. If you want to use the headers, you will need to solder them yourself.